574
FXUS62 KCHS 301516
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1116 AM EDT SUN MAR 30 2025
SYNOPSIS
RAIN AND THUNDERSTORM CHANCES INCREASE TODAY AND AGAIN MONDAY
AHEAD OF AN APPROACHING COLD FRONT. THE FRONT COULD LINGER
NEARBY MID-WEEK, BEFORE STRONGER HIGH PRESSURE PREVAILS LATE
NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
TODAY: ALOFT, A WEST/SOUTHWEST FLOW WILL PREVAIL WHILE H5 SHORTWAVE
ENERGY TRAVERSES OVER THE REGION. AT THE SFC, THE LOCAL AREA WILL
REMAIN ALONG THE WESTERN PERIPHERY OF ATLANTIC HIGH PRESSURE, WITH
LIGHT SOUTHEAST/SOUTH WINDS OCCURRING THROUGHOUT THE DAY. FORCING
ASSOCIATED WITH H5 SHORTWAVE ENERGY AND STRENGTHENING ISENTROPIC
LIFT ALONG WITH A NOTABLE INCREASE IN MOISTURE (PWATS APPROACHING
1.5 INCHES) WILL FAVOR PRECIP SPREADING ACROSS SOUTHEAST GEORGIA
LATE MORNING AND EVENTUALLY INTO SOUTHEAST SOUTH CAROLINA THIS
AFTERNOON, BUT NOT EVERYWHERE WILL RECEIVE RAIN AS THE GREATEST QPF
WILL BE OVER GEORGIA, WHERE 1/4 TO 1/2 INCH AMOUNTS ARE POSSIBLE.
FURTHER NORTH, THERE IS STILL SOME EVIDENCE OF A LOW-LVL SUBSIDENCE,
WHICH WILL LIKELY KEEP PRECIP AMOUNTS LOWER. STRONGEST INSTABILITY
WILL BE LOCATED ACROSS SOUTHERN AREAS AS WELL, AT LEAST INITIALLY,
FAVORING FEW TO SCATTERED THUNDERSTORMS THIS AFTERNOON. HOWEVER,
INSTABILITY SHOULD REMAIN SOMEWHAT LIMITED DUE TO CLOUDS (SBCAPE
LESS THAN 1000 J/KG), MID-LVL LAPSE RATES WILL REMAIN WEAK AND BULK
SHEAR WILL BE RATHER MODEST (20-25 KT), SUGGESTING MORE LOOSELY
ORGANIZED CONVECTION WITH A NEAR-ZERO THREAT FOR SEVERE WEATHER, BUT
A FEW STRONGER THUNDERSTORMS WITH GUSTY WINDS BEING POSSIBLE.
WARM AIR ADVECTION WILL COMPENSATE SOMEWHAT FOR THE EXTENSIVE CLOUD
COVER, AND AS SUCH HIGH TEMPS SHOULD PEAK IN THE MID TO PERHAPS
UPPER 70S AWAY FROM THE COAST. COASTAL COMMUNITIES WILL BE HELD DOWN
CLOSER TO 70F WITH A PERSISTENT ONSHORE FLOW OFF THE COOLER OCEAN
WATERS.
TONIGHT: WITH THE PASSAGE OF A SHORT WAVE THIS EVENING, AND THE
LOSS OF INSTABILITY WITHIN THE NOCTURNAL ENVIRONMENT, SHOWERS
AND ANY ISOLATED T-STORMS WILL COME TO AN END FROM THE SOUTHWEST
TO THE NORTHEAST AS THE NIGHT PROGRESSES. ADDITIONAL RAINFALL
AMOUNTS WILL GENERALLY BE NO MORE THAN 1/10 TO 1/4 INCH. AS THE
CONVECTION COMES TO AN END, LOW STRATUS/STRATOCUMULUS WILL
DEVELOP, AS A LOW LEVEL WARM FRONT LIFTS NORTH-NORTHEAST
THROUGH THE AREA. THIS ALONG WITH THE WET GROUNDS WILL LEAD TO
AT LEAST SOME FOG FORMATION. FOR NOW WE HAVE ADDED PATCHY FOG TO
THE ENTIRE AREA, MAINLY AFTER MIDNIGHT. LOW LEVEL WINDS MIGHT
BE TOO STRONG FOR DENSE FOG, BUT WITH SOME CHANCE FOR SEA FOG,
WE WILL NEED TO CLOSELY MONITOR THE SITUATION. GIVEN THE CHANCE
FOR FOG, AND THE FACT THAT MOST AREAS WERE COOLER THAN GUIDANCE
THE PAST TWO NIGHT TIME PERIODS, WE WENT CLOSER TO THE DEW
POINTS FOR ACTUAL LOWS. THIS YIELDS MIN TEMPERATURES IN THE
UPPER 50S TO NEAR 60F DEGREES.
SHORT TERM /MONDAY THROUGH WEDNESDAY/
MOST ACTIVE WEATHER DAY FOR THE SHORT/LONG TERM FALLS ON MONDAY,
WHERE THE REGION REMAINS IN THE WARM-SECTOR WELL OUT AHEAD OF AN
ADVANCING COLD FRONT. AREAS ALONG THE COAST MAY SEE THE CONTINUATION
OF PATCHY TO AREAS OF SEA/LAND FOG INTO AT LEAST THE LATE MORNING
HOURS, WITH PERSISTENT PARTLY TO MOSTLY CLOUDY SKIES EXPECTED
THROUGH MOST OF THE DAY. DESPITE THE CLOUDY CONDITIONS, WARM-AIR
ADVECTION IN THE LOW-MID LEVELS WILL ALLOW FOR TEMPERATURES TO RISE
UP INTO UPPER 70S TO MID 80S, WITH DEWPOINTS REMAINING FAIRLY STEADY
IN THE MID 60S. THIS WILL RESULT IN BUILDING INSTABILITY THROUGHOUT
THE DAY, PEAKING IN THE 1000-2000 J/KG RANGE WITH SHEAR REMAINING
DECENT AT AROUND 30-40 KNOTS BEFORE CIN ERODES BY THE EARLY/MID
AFTERNOON HOURS. WHILE MOST GUIDANCE DOES NOT SHOW DIURNALLY DRIVEN
SHOWERS/THUNDERSTORMS FORMING DUE TO CONVECTIVE TEMPERATURES NOT
BEING REACHED, LIKELY DUE TO CLOUD COVERAGE REMAINING HIGH, CAN'T
RULE OUT A STRAY SHOWER/STORM OUT AHEAD OF THE EXPECTED SQUALL LINE
MOVING TOWARDS THE AREA. GIVEN MARGINAL SHEAR AND RATHER WEAK FLOW
ALOFT, THESE STORMS LIKELY WOULDN'T ABLE TO SUSTAIN THEMSELVES FOR
LONG, THOUGH A COLLAPSING UPDRAFT COULD RESULT IN STRONG WINDS GIVEN
DCAPE VALES OF UP TO NEAR 1000 J/KG.
THERE REMAINS TIMING DIFFERENCES AMONGST THE GLOBAL AND HIGH-
RESOLUTION GUIDANCE, THOUGH IN THESE SCENARIOS THE HIGH-RESOLUTION
GUIDANCE GENERALLY DOES BETTER. THE SQUALL LINE IS EXPECTED TO PUSH
INTO OUR EASTERN GEORGIA COUNTIES (JENKINS/CANDLER/TATTNALL) BETWEEN
2 AND 4 PM, REACHING THE I-95 CORRIDOR BETWEEN 4 AND 6 PM, AND THE
CHARLESTON TRI-COUNTY REGION BETWEEN 6 AND 8 PM. GIVEN THE WARM
TEMPERATURES RESULTING IN FREEZING LEVELS AT ABOUT 12 KFT, LARGE
HAIL (> 1 INCH) MAY BE DIFFICULT TO GET REACHING THE SURFACE, THOUGH
SMALL HAIL CAN'T BE RULED OUT. THE MAIN THREAT, AS IS COMMON WITH
SQUALL LINE, ARE STRONG DAMAGING WIND GUSTS IN EXCESS OF 60 MPH FOR
SECTIONS OF THE LINE THAT REMAIN PREDOMINANTLY SHEAR-BALANCED AND
NOT UNDERCUT BY THE COLD POOL.
SPC INCREASED THE RISK FOR SEVERE THUNDERSTORMS ACROSS THE AREA INTO
LEVEL 3 OUT OF 5, PRIMARILY DRIVEN BY THEIR UPGRADE TO 10%
PROBABILITIES FOR TORNADOES. LOCALLY, JUST NOT CONFIDENT IN THE
UPGRADE IN TORNADO POTENTIAL. LOOKING AT THE FIXED-LAYER STP
PROBABILITIES FROM THE HREF, THE MEANS DECREASE AS THE STORMS
TRAVERSE INTO EASTERN SOUTH CAROLINA AND EASTERN GEORGIA. AS WAS
MENTIONED BEFORE, IT'S ALSO LOOKING LIKE WE'LL BE FAIRLY CLOUDY
THROUGH MUCH OF THE DAY, WHICH WOULD MEAN WE WON'T GET THE LOW-LEVEL
CAPE AND LAPSE RATES NEEDED FOR THE INCREASED TORNADO POTENTIAL,
HINTED AT BY BOTH THE RAP AND HRRR SHOWING SIGTOR REMAINING IN
THE 1-2 CATEGORY. THE HRRR NEURAL NETWORK AND CSU MLP BOTH SHOW
A SIMILAR SCENARIO, WITH TORNADO PROBABILITIES LOWERING AS
STORMS TRAVERSE INTO THE SOUTHEASTERN SC & GA. REGARDLESS,
ISOLATED TO SCATTERED TORNADOES DO LOOK TO BE POSSIBLE, SO BE
SURE TO HAVE A WAY TO RECEIVE WARNINGS AND A PLAN OF ACTION
SHOULD A SEVERE OR TORNADO WARNING BE ISSUED FOR YOUR AREA.
SHOWERS AND THUNDERSTORMS PUSH OFF INTO THE NEAR AND OFFSHORE WATERS
THROUGHOUT THE REST OF THE EVENING HOURS, WITH THE "COLD" FRONT
MOVING THROUGH PRIOR TO DAYBREAK ON TUESDAY. 24 HOUR RAINFALL
PROBABILITIES FROM THE NBM FOR 0.10" INCHES REMAIN ARE IN THE 80S
ALONG THE COASTAL REGIONS, RISING INTO THE UPPER 80S TO LOWER 90S
ACROSS THE INLAND AREAS. NBM PROBABILITIES FOR THE SAME REGIONS FOR
A QUARTER INCH ARE IN THE 40S ALONG THE COAST AND 60-70S INLAND,
WITH PROBABILITIES FOR HALF AN INCH DROPPING INTO THE 20S ALONG THE
COAST AND 30-40 FOR INLAND AREAS.
A SURFACE HIGH PRESSURE BUILDS IN FROM THE NORTH THROUGHOUT THE DAY
ON TUESDAY, WITH UPPER LEVEL RIDGING TAKING PLACE ALOFT. HIGHS ARE A
TOUCH COOLER, THOUGH STILL IN THE UPPER 70S TO LOWER 80S.
WARM AIR ADVECTION ON WEDNESDAY MAY RESULT IN A FEW SCATTERED
SHOWERS, THOUGH RAINFALL AMOUNTS WILL REMAIN ON THE LOW SIDE (<
0.05"). OTHERWISE WEDNESDAY IS LOOKING TO BE PARTLY TO MOSTLY
CLOUDY, WITH AFTERNOON HIGHS IN THE LOWER TO UPPER 80S.
LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/
THE LONG TERM CONTINUES TO REMAIN LARGELY WARM AND DRY AS A STRONG
UPPER LEVEL RIDGE SETS UP JUST OFF TO OUR SOUTH. ENSEMBLE
SITUATIONAL AWARENESS TABLES SHOW THE STRONG UPPER LEVEL RIDGE WILL
LIKELY PRODUCE ABNORMALLY HIGH SURFACE TEMPERATURES, WITH THE
DETERMINISTIC NBM COMING IN MUCH CLOSER TO THE 50TH PERCENTILE OF
AVAILABLE GUIDANCE. DAILY HIGHS IN THE MID 80S TO LOWER 90S ARE
EXPECTED FOR INLAND AREAS THURSDAY THROUGH SUNDAY, WITH COASTAL
AREAS A TOUCH COOLER IN THE UPPER 70S TO LOWER 80S. NEW RECORD DAILY
HIGH MINIMUMS ARE WITHIN 3 DEGREES OF THE CURRENT FORECAST THURSDAY
THROUGH SATURDAY. RECORD DAILY HIGHS ARE WITHIN 2 DEGREES ON
SATURDAY AS THE RECORDS ARE A TOUCH COOLER, WITH THE NUMBERS TO BEAT
BEING 89 DEGREES AT THE CHARLESTON AIRPORT AND 90 DEGREES AT THE
SAVANNAH AIRPORT.
AVIATION /15Z SUNDAY THROUGH THURSDAY/
KCHS/KJZI: VFR CONDITIONS WILL PREVAIL INTO THE AFTERNOON, WITH
LIGHT OR CALM WINDS TO SLOWLY INCREASE LATER THIS MORNING, AND
BECOME A BIT GUSTY THIS AFTERNOON DURING THE WARMEST PART OF THE
DAY. SHOWERS ASSOCIATED WITH A WEAK COASTAL TROUGH, DEEPER
MOISTURE, AND A SHORT WAVE ALOFT, WILL CAUSE THE RISK FOR SOME
SHOWER ACTIVITY DURING THE AFTERNOON AND EVENING. FLIGHT
RESTRICTIONS MIGHT OCCUR, BUT THE HIGHER CHANCES FOR FLIGHT
RESTRICTIONS WILL BE TONIGHT AS THE SHOWERS END, AND A
STRENGTHENING LOW LEVEL INVERSION DEVELOPS, TRAPPING
CONSIDERABLE MOISTURE UNDERNEATH. FOR NOW WE HAVE MVFR AT ALL
TERMINALS, BUT IFR OR LIFR IS LIKELY, THE RESULT OF LOWERING
CEILINGS AND FOG.
KSAV: VFR CONDITIONS WILL PREVAIL INTO THE AFTERNOON, WITH
LIGHT OR CALM WINDS TO SLOWLY INCREASE LATER THIS MORNING, AND
BECOME A BIT GUSTY THIS AFTERNOON DURING THE WARMEST PART OF THE
DAY. SHOWERS ASSOCIATED WITH A WEAK COASTAL TROUGH, DEEPER
MOISTURE, AND A SHORT WAVE ALOFT, WILL RESULT SHRA/-SHRA AT
TIMES THROUGHOUT THE DAY, PERHAPS EVEN A TSRA. FLIGHT
RESTRICTIONS MIGHT OCCUR, BUT THE HIGHER CHANCES FOR FLIGHT
RESTRICTIONS WILL BE TONIGHT AS THE SHOWERS END, AND A
STRENGTHENING LOW LEVEL INVERSION DEVELOPS, TRAPPING
CONSIDERABLE MOISTURE UNDERNEATH. FOR NOW WE HAVE MVFR AT ALL
TERMINALS, BUT IFR OR LIFR IS LIKELY, THE RESULT OF LOWERING
CEILINGS AND FOG.
EXTENDED AVIATION OUTLOOK: FLIGHT RESTRICTIONS CONTINUE TO
REMAIN POSSIBLE MONDAY MORNING DUE TO BOTH SEA AND LAND FOG,
WITH MVFR AND IFR CIGS EXPECTED AS A LINE OF THUNDERSTORMS MOVES
THROUGH MONDAY AFTERNOON INTO THE EVENING HOURS.
MARINE
TODAY: A 1030 MB HIGH CENTERED EAST OF BERMUDA WILL EXTEND
ACROSS THE IMMEDIATE WATERS, WITH THE ASSOCIATED RIDGE AXIS JUST
TO THE NORTH EARLY ON SAGGING SOUTHWARD THROUGH THE DAY. THE
PRESSURE GRADIENT REMAINS RATHER WEAK ACROSS LOCAL WATERS, BUT
SUFFICIENT TO GENERATE SE WINDS NO MORE THAN 10-15 KT. SEAS
WILL BE A MIX OF SWELLS AND WIND DRIVEN WAVE, RESULTING IN
SIGNIFICANT WAVE HEIGHTS OF 3-5 FT ON THE WATERS OUT 20 NM.
FURTHER OFFSHORE, A SMALL CRAFT ADVISORY IS IN PLACE FOR 6 FT
SEAS ON THE OUTER GEORGIA WATERS, BUT THIS IS BASED MAINLY ON
THE CONSENSUS OF THE MODELS. MARINERS WILL EXPERIENCE SOME
T-STORMS THIS AFTERNOON, MAINLY SOUTH OF EDISTO, ALTHOUGH GIVEN
THE SMALL AMOUNT OF INSTABILITY AND SHEAR, THE RISK FOR ANY
SEVERE STORMS IS CLOSE TO ZERO. KEEP IN MIND THOUGH THAT
LIGHTNING STRIKES WILL OCCUR.
TONIGHT: THE ATLANTIC HIGH PULLS FURTHER EAST, AS A COLD FRONT
DROPS INTO THE TENNESSEE AND LOWER MISSISSIPPI VALLEYS. WINDS
TURN MORE SOUTHERLY, BUT ONCE AGAIN NO GREATER THAN 10 OR 15 KT,
WHILE SEAS ARE 5 FEET OR LESS. LINGERING T-STORMS EARLY ON WILL
COME TO AN END, FOLLOWED BY THE RISK FOR SEA FOG, WITHIN A WARM
AND MOIST AIR MASS ATOP THE SOMEWHAT COOLER WATERS. WE HAVE
INCLUDED PATCHY FOG IN THE FORECAST AS A A RESULT, AND WE'LL
MAINTAIN A WEATHER WATCH FOR POSSIBLE DENSE FOG AND A DENSE FOG
ADVISORY.
MONDAY/TUESDAY: MODELS SHOW AT LEAST PATCHY SEA FOG CONTINUING INTO
THE EARLY AFTERNOON HOURS, THOUGH BREEZY SOUTHEAST GRADIENT WINDS
OUT AHEAD OF AN APPROACHING COLD FRONT DROPS CONFIDENCE A TOUCH.
WIND SPEEDS CONTINUE TO REMAIN JUST BELOW SMALL CRAFT CRITERIA, WITH
CHANCES FOR 6 FOOT WAVES CONTINUING IN THE OFFSHORE GA WATERS,
THOUGH IT LOOKS TO REMAIN CONFINED TO A SMALL ENOUGH PORTION OF THE
ZONE TO AVOID ISSUING A SMALL CRAFT ADVISORY AT THIS TIME.
AFTERNOON SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE EXPECTED
TO PUSH THROUGH INTO THE EARLY OVERNIGHT HOURS ON TUESDAY. WINDS
WILL BE STARTING OUT OF THE WEST DURING THE MORNING, VEERING TO THE
NORTH-NORTHEAST IN THE AFTERNOON, AND CONTINUING TO VEER TO THE EAST
INTO THE EVENING HOURS.
WEDNESDAY: SURFACE HIGH PRESSURE BUILDS IN FROM THE NORTH, RESULTING
IN EAST WINDS BECOMING SOUTHEASTERLY THROUGHOUT THE DAY. MAY SEE SOME
ISOLATED SHOWERS DEVELOP, THOUGH CONFIDENCE REMAINS LOW AT THIS
TIME WITH PROBABILITIES FOR RAIN IN THE 20-30% RANGE.
THURSDAY: WARM AND DRY CONDITIONS RETURN.
EQUIPMENT
THE KCLX RADAR REMAINS OFFLINE FOR DOME MAINTENANCE THROUGH
APRIL 1, 2025. RADAR DATA WILL NOT BE AVAILABLE DURING THIS
TIME. USERS ARE URGED TO USE ADJACENT WSR-88D SITES WHICH ALSO
COVER MUCH OF SOUTHEAST SOUTH CAROLINA, SOUTHEAST GEORGIA AND
THE ADJACENT COASTAL WATERS. THESE INCLUDE:
KCAE - COLUMBIA, SC
KLTX - WILMINGTON, NC
KJAX - JACKSONVILLE, FL
KVAX - MOODY AFB, GA
KJGX - ROBBINS AFB, GA
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 PM EDT THIS AFTERNOON FOR AMZ374.
NEAR TERM...DPB
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...DPB
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